Relationship between root densities and extractable organic C (EOC) at the Calhoun Critical Zone Observatory. Root density is expressed as the fraction of each 1-cm depth interval below 20 cm containing roots; only forested soils are depicted. A significant interaction between land use and root density (P = 0.047) indicates a greater sensitivity of old-growth soil EOC to root density than in regenerating pine soils. DOI: https://doi.org/10.1525/elementa.287.f6